Digestive System Processes and Chemical Digestion
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Questions and Answers

What does a clearance value (C) of 0 ml/min indicate about a substance?

  • The substance is present in urine.
  • The substance is completely reabsorbed or not filtered. (correct)
  • The substance is completely filtered from the plasma.
  • The substance is secreted by the renal tubules.

    • Which of the following is a normal component of urine?

  • Creatinine (correct)
  • White blood cells
  • Glucose
  • Ketone bodies

    • What does a clearance value (C) greater than 125 ml/min suggest about a substance?

  • The substance is secreted by the renal tubules. (correct)
  • The substance is completely reabsorbed.
  • The substance is freely filtered but not secreted.
  • The substance is partially cleared from the plasma.

    • Which part of the urinary system is responsible for temporarily storing urine?

    <p>Bladder</p> Signup and view all the answers

    What type of muscle comprises the internal urethral sphincter?

    <p>Smooth muscle</p> Signup and view all the answers

    What is the primary function of ureters in the urinary system?

    <p>Conveying urine from kidneys to the bladder</p> Signup and view all the answers

    How does the presence of albumin in urine typically present in individuals with hypertension?

    <p>Signifying potential kidney damage</p> Signup and view all the answers

    What structural characteristic of urine is due to the presence of the pigment urochrome?

    <p>Color</p> Signup and view all the answers

    What is the primary function of the myogenic mechanism in glomerular filtration?

    <p>Increases filtration rate during low systemic blood pressure.</p> Signup and view all the answers

    Which process is primarily responsible for the reabsorption of glucose and amino acids in the nephron?

    <p>Proximal convoluted tubule action.</p> Signup and view all the answers

    How does angiotensin II contribute to the maintenance of systemic blood pressure?

    <p>Triggers vasoconstriction of arterioles.</p> Signup and view all the answers

    What role does the macula densa play in the tubuloglomerular feedback mechanism?

    <p>Inhibits its own release of vasoconstrictors when GFR is low.</p> Signup and view all the answers

    What effect does the sympathetic nervous system have when systemic blood pressure drops?

    <p>Promotes systemic vasoconstriction.</p> Signup and view all the answers

    Which structure in the nephron allows water to exit but not sodium in its ascending limb?

    <p>Loop of Henle.</p> Signup and view all the answers

    Which of the following statements about tubular reabsorption is correct?

    <p>The majority of electrolyte reabsorption occurs in the PCT.</p> Signup and view all the answers

    What is the typical volume of filtrate formed per minute by both kidneys?

    <p>125 ml/min.</p> Signup and view all the answers

    What is the role of the antidiuretic hormone (ADH) in the formation of concentrated urine?

    <p>Increases permeability of the collecting ducts to water</p> Signup and view all the answers

    How does aldosterone affect renal function?

    <p>Stimulates reabsorption of sodium and water</p> Signup and view all the answers

    Which statement correctly describes the countercurrent multiplier mechanism?

    <p>It creates a medullary osmotic gradient</p> Signup and view all the answers

    What primarily determines renal clearance of a substance?

    <p>The volume of plasma cleared of a substance per minute</p> Signup and view all the answers

    How does dehydration affect ADH levels and urine output?

    <p>Increases ADH, leading to concentrated urine</p> Signup and view all the answers

    What is the primary effect of osmotic diuretics?

    <p>Inhibit reabsorption of water and increase urine output</p> Signup and view all the answers

    Which of the following substances can be cleared from plasma by tubular secretion?

    <p>Urea</p> Signup and view all the answers

    What happens to urine volume when ADH secretion is inhibited?

    <p>Increase in dilute urine volume</p> Signup and view all the answers

    Which mechanism is primarily responsible for preserving the medullary osmotic gradient?

    <p>Countercurrent exchanger</p> Signup and view all the answers

    What role does PTH (parathyroid hormone) play in the kidneys?

    <p>Stimulates calcium reabsorption in the distal convoluted tubule</p> Signup and view all the answers

    Study Notes

    Digestive System

    • Digestive Processes:
      • Ingestion: Taking food into the digestive tract.
      • Propulsion: Moving food through the digestive tract, including swallowing and peristalsis.
      • Mechanical Breakdown: Mastication (chewing), mixing food with saliva by the tongue, churning in the stomach, and segmentation.
      • Digestion: Enzymes break down complex food into simpler molecules.
      • Absorption: Passage of digested food from the lumen of the GI tract into blood or lymph.
      • Defecation: Elimination of indigestible substances.

    Chemical Digestion

    • Carbohydrates:

      • Salivary amylase in saliva breaks down starch into oligosaccharides.
      • Pancreatic amylase further breaks down starch and glycogen into oligosaccharides and disaccharides.
      • Brush border enzymes convert oligosaccharides and disaccharides into monosaccharides.
      • Monosaccharides are absorbed via secondary active transport and exit via facilitated diffusion into capillaries.

    • Proteins:

      • Pepsinogen, activated to pepsin in the stomach, breaks proteins into polypeptide chains.
      • Pancreatic enzymes (trypsin, chymotrypsin, carboxypeptidase) further break down polypeptides into smaller chains.
      • Brush border enzymes (peptidases) break them into amino acids.
      • Amino acids are absorbed via secondary active transport and exit via facilitated diffusion into capillaries.

    • Lipids:

      • Emulsification by bile salts in the duodenum breaks large fat globules into smaller droplets, increasing surface area for lipase action.
      • Pancreatic lipase hydrolyzes triglycerides into monoglycerides and fatty acids.
      • Micelle formation: Products of fat digestion (monoglycerides and fatty acids) combine with bile salts to form tiny micelles. These ferry contents to the epithelial cells.
      • Diffusion: Fatty acids and monoglycerides diffuse into epithelial cells.
      • Chylomicron formation: Fatty acids and monoglycerides are recombined and packaged with other fatty substances and proteins into chylomicrons.

    Peritoneum and Digestive Activity

    • Peritoneum: Serous membrane lining the abdominal cavity, including visceral (covering organs) and parietal (lining the wall) peritoneum.
    • Mesentery: Double layer of peritoneum routing blood vessels, lymphatics, and nerves, holding organs in place.
    • Intrinsic Nerve Supply (Short Reflexes): Controlled by the enteric nervous system (submucosal and myenteric nerve plexuses).
    • Extrinsic Nerve Supply (Long Reflexes): Linked to the central nervous system (CNS) via afferent and efferent fibers, controlling digestive activity (sympathetic inhibits, parasympathetic stimulates).

    Oral Cavity (Saliva, Chewing & Swallowing)

    • Saliva Function: Cleanses the mouth, dissolves food chemicals for taste, moistens food, forms a bolus, and begins starch digestion with enzymes.
    • Saliva Composition: 97-99.5% water, electrolytes, digestive enzymes (salivary amylase), and proteins.
    • Chewing/Mastication: The process of mechanical breakdown of food, with the help of teeth, and tongue.
    • Swallowing/Deglutition: The process that takes food from buccal to esophagus, using different phases (buccal, pharyngeal & esophageal).

    Gastric Gland and Secretion

    • Mucosal Barrier: Protects the stomach lining from harsh digestive conditions (thick layer of bicarbonate-rich mucus, tight junctions). Damaged cells are quickly replaced.
    • Parietal Cells: Secrete hydrochloric acid (HCl) for protein denaturation and pepsin activation, and intrinsic factor for vitamin B12 absorption.
    • Chief Cells: Secrete pepsinogen, which is activated to pepsin by HCl and pepsin itself (positive feedback).
    • Enteroendocrine Cells: Secrete gastrin for regulating stomach secretion and motility.
    • Phases of Gastric Secretion: Cephalic phase (before food), gastric phase (food is in the stomach), and intestinal phase (in the small intestine).

    Small Intestine Modifications

    • Circular folds (plicae circulares): Permanent folds in the mucosa and submucosa that slow movement and provide more absorption surface.
    • Villi: Finger-like projections of the mucosa, containing capillaries and lacteals for nutrient absorption.
    • Microvilli: Microscopic projections on the surface of villi (brush border) with enzymes for further digestion.

    Liver and Pancreatic Juice

    • Liver Histology: Structure of liver, including portal triad (hepatic artery, portal vein, bile duct) and hepatocytes.
    • Hepatocyte Functions: Processing blood-borne nutrients, storing fat-soluble vitamins, performing detoxification, and producing bile for emulsification.
    • Pancreas: Exocrine function (pancreatic juice) to neutralize chyme. Contains enzymes like proteases, amylase, lipases and nucleases. The enzymes are secreted in inactive form and activated in the small intestine.

    Large Intestine

    • Bacterial Flora: Assists with energy recovery from indigestible foods (such as cellulose) through fermentation.
    • Defecation: The propulsion of feces to the anus, stimulated by stretch receptors in the rectum.

    Metabolism

    • Carbohydrates: Dietary sources (starch, sugars, cellulose) used for fuel (ATP production) and stored as glycogen/fat.
    • Lipids: Dietary sources (triglycerides, saturated/unsaturated fats) used for fuel, stored as adipose tissue.
    • Proteins: Dietary sources (complete & incomplete proteins) used for structural components, functional molecules (enzymes, hormones, antibodies), and fuel when carbohydrates and fats are limited.
    • Carbohydrate Metabolism Pathways: Glycolysis, Krebs Cycle, and Electron Transport Chain to produce ATP.

    Urinary System

    • Kidney Functions: Regulating water volume and solute concentration, ensuring acid-base balance, removing metabolic wastes, and endocrine functions (Renin, Erythropoietin, Vitamin D).

    • Nephron Structure:

      • Renal Corpuscle: Glomerulus (capillaries) and glomerular capsule (Bowman's capsule).
      • Renal Tubule & Collecting Duct: Proximal convoluted tubule (PCT), nephron loop (descending & ascending limbs), distal convoluted tubule (DCT) and collecting ducts.

    • Capillary Beds Associated with Nephrons: Glomerulus (filtration); peritubular capillaries; and vasa recta (for concentration).

    • Juxtaglomerular Complex (JGC): Macula densa cells and granular (JG cells) monitor NaCl and blood pressure to regulate glomerular filtration rate (GFR).

    • Renal Processes: Glomerular filtration (filtration), tubular reabsorption (reclaiming essential materials), and tubular secretion (removal of waste).

    • Tubular Reabsorption:

    • Tubular secretion Important way for kidneys to clear plasma of substances such as drugs or metabolites or nitrogenous wastes or excess K+.

    • Urine Formation: Formation and concentration of urine dependent on levels of ADH and amount of water intake.

    • Renal Clearance: Volume of plasma the kidneys clear of a substance in a given time (inulin, creatinine, etc.).

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    Study Guide - Lecture Exam 3 PDF

    Description

    Explore the intricate processes of the digestive system, including ingestion, propulsion, and absorption. This quiz also covers the chemical breakdown of carbohydrates through various enzymes, detailing how food is converted into absorbable molecules.

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